1. Field of the Invention
This invention relates to a radiation image recording and read-out method and apparatus, wherein a radiation image is stored on a stimulable phosphor sheet, the stimulable phosphor sheet, on which the radiation image has been stored, is exposed to stimulating rays, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to radiation, the emitted light is detected, and the radiation image is thereby read out from the stimulable phosphor sheet and converted into an electric signal. This invention particularly relates to an improvement in an erasing light source.
2. Description of the Related Art
It has been proposed to use stimulable phosphors in radiation image recording and reproducing systems. Specifically, a radiation image of an object, such as a human body, is recorded on a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet). The stimulable phosphor sheet, on which the radiation image has been stored, is then exposed to stimulating rays, such as a laser beam, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal. The image signal is then processed and used for the reproduction of the radiation image of the object as a visible image on a recording material. The radiation image recording and reproducing systems described above are referred to as computed radiography (CR).
The applicant proposed built-in types of radiation image recording and read-out apparatuses, comprising: (i) circulation and conveyance means for conveying at least one stimulable phosphor sheet along a circulation path, (ii) an image recording section, which is located in the circulation path and in which a radiation image of an object is stored on the stimulable phosphor sheet, (iii) an image read-out section, which is located in the circulation path and in which the radiation image is read out from the stimulable phosphor sheet, and (iv) an erasing section, which is located in the circulation path and in which energy remaining on the stimulable phosphor sheet after the radiation image has been read out therefrom is released. The built-in types of radiation image recording and read-out apparatuses are disclosed in, for example, U.S. Pat. Nos. 4,543,479 and 4,851,679, and Japanese Unexamined Patent Publication No. 3(1991)-238441. With the proposed built-in types of radiation image recording and read-out apparatuses, the stimulable phosphor sheet is utilized repeatedly and is processed efficiently.
As for the radiation image recording and read-out apparatuses described above, from the point of view of keeping the emitted light detection time short, reducing the size of the apparatus, and keeping the cost low, it has been proposed to utilize a line sensor comprising a charge coupled device (CCD) image sensor, or the like, as photoelectric read-out means. The utilization of the line sensor as the photoelectric read-out means is disclosed in, for example, Japanese Unexamined Patent Publication Nos. 60(1985)-111568, 60(1985)-236354, and 1(1989)-101540.
Basically, the radiation image recording and read-out apparatuses of such types comprise:
i) a read-out unit comprising (a) stimulating ray irradiating means for linearly irradiating stimulating rays onto an area of a stimulable phosphor sheet, on which a radiation image has been stored, the stimulating rays causing the stimulable phosphor sheet to emit light in proportion to an amount of energy stored thereon during its exposure to radiation, and (b) a line sensor, which comprises a plurality of photoelectric conversion devices arrayed along the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays, and
ii) sub-scanning means for moving the stimulable phosphor sheet with respect to the read-out unit and in a direction (a sub-scanning direction), which is approximately normal to a length direction of the linear area of the stimulable phosphor sheet exposed to the linear stimulating rays (a main scanning direction).
In particular, in cases where the radiation image recording and read-out apparatuses are constituted such that the stimulable phosphor sheet is kept stationary, and the read-out unit is moved in the sub-scanning direction, the sizes of the radiation image recording and read-out apparatuses as a whole are capable of being kept small. As an example of the radiation image recording and read-out apparatus having the constitution described above, in order for energy, which remains on the stimulable phosphor sheet after the radiation image has been read out from the stimulable phosphor sheet, to be released, there has heretofore been proposed a radiation image recording and read-out apparatus, wherein an erasing light source is located on the side backward from the read-out unit, and erasing light is irradiated simultaneously to the entire surface of the stimulable phosphor sheet. As a different example of the radiation image recording and read-out apparatus having the constitution described above, in order for energy, which remains on the stimulable phosphor sheet after the radiation image has been read out from the stimulable phosphor sheet, to be released, there has heretofore been proposed a radiation image recording and read-out apparatus, wherein an erasing light source is located within the read-out unit, and the read-out unit is moved in order to irradiate erasing light successively to the entire surface of the stimulable phosphor sheet. The examples of the radiation image recording and read-out apparatuses described above are proposed in, for example, Japanese Unexamined Patent Publication No. 63(1988)-189855.
However, with the proposed radiation image recording and read-out apparatus, wherein the erasing light source is located on the side backward from the read-out unit, and the erasing light is irradiated simultaneously to the entire surface of the stimulable phosphor sheet in order to release energy remaining on the stimulable phosphor sheet, the read-out unit located between the stimulable phosphor sheet and the erasing light source intercepts the erasing light. Therefore, the problems occur in that the erasing light cannot be uniformly irradiated to the entire surface of the stimulable phosphor sheet.
With the proposed radiation image recording and read-out apparatus, wherein the erasing light source is located within the read-out unit, and the read-out unit is moved in order to irradiate the erasing light successively to the entire surface of the stimulable phosphor sheet, both the image read-out means and the erasing light source are accommodated within the read-out unit. Therefore, the problems occur in that the constitution of the read-out unit cannot be kept simple, and the size of the read-out unit cannot be kept small.